bwnbwn - 7:18 pm on Jul 3, 2012 (gmt 0)
There was an update on Sat. 3oth. I think it is an anchor text update. This happened about 2 months ago same drop on an ecommerce site. Site lost wholesale and picked up cheap as the main target keyword. Look at the serps were your site is now ranking see if your primary term has changed.